Paul Randal is a great presented in the SQL Server/database space and he usually draws large crowds. Some of it is his knowledge, but he's also very entertaining and I think that goes a long way as well. I noticed that he recently wrote a post on Public Speaking, which I think has some great advice.
There are two things that I'd like to comment on. First, take feedback well. You won't please everyone, but before you dismiss someone's complaint, take a moment to look at it and consider if there is something to learn there. You might find something you can improve on, but don't feel that you have to. You won't please everyone, so be sure that you don't feel you have to change your delivery to address every piece of feedback.
The other thing is branding. You want to be careful about pushing yourself or your work in the presentation. A casual mention is fine, show the URL for your site, your logo, etc. I typically open my presentation by showing the various things I'm involved with, I might make a comment about one of them so that people know what they are, but I don't spend more than a minute on them. Let your work speak for itself.
It's also better to maybe mention things at the end if possible.
I'd recommend you read the post if you are interested in speaking at all.